DE4339811C2 - Dosing device for volumetric dosing of a liquid additive - Google Patents

Abstract

The invention comprises a metering device (10) for volumetric dispensing of a liquid additive which is added in a specific volume ratio to a liquid flowing in a first tube line (11), in particular drawn-off blood, this addition being effected via a second tube line (12) which opens directly or indirectly into the first tube line. The metering device (10) according to the invention is intended in particular for volumetric dispensing of an anticoagulant liquid (ACD) or a sedimentation accelerator in a system for collection and retransfusion of autologous blood, which system has a tube or pipe section extending downstream of the junction point (14), and also a drip chamber (18) connected downstream of the drip tube (16), and a light barrier (30) whose direction of action is transverse to the direction in which the drops fall. In order to rule out the possibility of incorrect dispensing resulting from changing viscosities of the liquid flowing in the first tube line (11) and associated changes in the size of the drops, it is proposed according to the invention to provide two electrically controllable valve means (22, 23), of which in each case one is included in one of the two tube lines (11, 12), and to control these valve means (22, 23) alternately by means of a counting and controlling unit (CPU, RAM) so that in each case only one of the two aforesaid tubes (11, 12) is switched on-line at any one time. The liquid remaining in the drip tube (16) due to the capillary effect in this case provides for a constancy of volume between drops falling at the lower end of the drip tube (16) and additive being metered in at the upper end of the drip tube (16). <IMAGE>

Description

The invention relates to a metering device for volumetric metering of a liquid additive, the fluid flowing in a first hose line via a second hose line in a certain volume ratio is added. Such a metering device is used in particular within a Systems for collection and retransfusion of autologous blood used to the suctioned off during an operation or the like and for Retransfusion provided an anticoagulant or a blood sample Add sedimentation accelerator.

A system for the collection and retransfusion of autologous blood is known for example from EP 0 438 703 A1. In the known system a collecting vessel is pressurized with a vacuum which is used to by means of a hose connected to the collecting vessel blood from a Operating field, d. H. a patient's body. The vacuumed Blood, known as drainage blood, flows through the tubing and passes a quantity metering device before it drips into the collection container. Upstream of the quantity metering device is a Y-shaped switch or Connection point arranged, into which a second hose opens, which with a Reservoir for an anticoagulant fluid and / or a Sedimentation accelerator is connected. Between the reservoir for the Anticoagulant liquid and the Y-shaped switch  there is a valve means that over the amount metering device mentioned can be controlled.

A device for filling a container with a mixture of various liquids is also known from DE 39 10 992 A1. Around Mixtures of several liquids with any mixing ratio and A metering pump is able to produce in the desired quantity Use whose other. Intake opening of several liquid-carrying lines are connected, each with a valve for optional opening and locking have the line. There is also a programmable control device provided, which allows the valves to be alternated for a particular one Time that a desired flow rate of the respective liquid corresponds to switching to the open state.

In addition, metering devices are known which operate on the principle of Work drop counting. With such metering devices, the liquid of a measuring or to be monitored, flowing in a hose Drip chamber fed with a light barrier. An Indian Drip chamber dropping liquid drops interrupts the light beam Light barrier and thus generates a counting pulse, which is used for further evaluation can be sent to a microprocessor or the like. A disadvantage of this type of Volume measurement of a flowing liquid is that the measurement result all the more the more inaccurate the greater the viscosity fluctuations, the liquid to be measured subject to. This is because of the changing kinematic toughness (Viscosity) and changing density a change in the volume of a with each drop. Since only the absolute number of drops dropped, this leads to the fact that the actual volumetric mixing ratio changes in the case where a certain number of drops dropped to a certain volume Additive is added, for example, after a certain number of fallen drops from the Quantity metering a signal is generated by means of which in the  Hose line arranged to the reservoir of the anticoagulant liquid itself subsequent valve means controlled and for a certain time cross section is opened.

On the other hand, the principle of volume determination using the drip chamber and Photoelectric switch cheap and easy to implement and work - at least as far as Photoelectric sensor part is affected - contactless, which is particularly the case with Patient blood processing equipment and devices made from hygienic Reasons is highly desirable.

The invention is therefore based on the object of a metering device for volumetric dosing of a liquid additive as described a fluid flowing in a first hose line, especially blood, through a second hose line in a particular one Volume ratio should be added, so that despite the Use of a drip chamber and a light barrier for drop counting and thus indirect volume determination of the flowing in the first hose line Fluids a metering of the additive to be added, in particular one Anticoagulant fluid, in a fixed volume ratio, without the dosing due to changing viscosities of the first Hose line flowing liquid is falsified.

This object is achieved according to the invention with the in claim 1 specified features.

The invention is based on the finding that in the drip chamber leading common hose or pipe section that is in shape a drip pipe is formed, due to the capillary action, a certain volume of fluid always remains.

Now the second hose line carrying the additive to be added is by means of the valve means switched so that additive can and will flow into the drip pipe at the same time the first hose line is interrupted by the other valve means, so that corresponds to the one moving into the drip pipe  Volume of additive the volume of the drop leaving the drip tube. If the mixing ratio between additive and primary fluid, for example blood, expressed in integer multiples of drops, for example, one drop of additive per seven drops of blood, one has Viscosity change and a resulting changed size of a single drop has no influence on the overall mixing ratio, because for example with a larger drop leaving the drip tube accordingly, a larger amount of additive is drawn into the drip pipe.

In a preferred embodiment of the invention, the valve means are one 4/2-way valve. The 4/2-way valve is preferably with a Provide spring preload so that the valve is the first in its rest position Hose line switches to continuity and the second, the additive leading Hose line is blocked. The conditions are in the switched state then vice versa, so that the first hose line is blocked and the second Hose line is unlocked.

In a further preferred embodiment, the valve means are one 3/2-way valve, so that the second hose line in the valve indirectly in the first hose line opens. In other words, the connections of the 3/2-way valve switched so that the first hose line in the spring-centered The valve is in the rest position directly on the drip pipe, while the second, the hose carrying additive is blocked. In the switched state the relationships are reversed, so that the second, the additive leading hose line now connected directly to the drip pipe and the first hose line is blocked.

In a further, technically somewhat more complex variant provided to combine the valve means in a 3/3-way valve, the has a spring-centered central position in which both hose lines  are locked. This additional position offers the advantage that both Hose lines can be blocked, for example if the one blood collection container is to be replaced.

In a further preferred embodiment, the counting and Control unit of the dosing device, a central processing unit (CPU) and further a freely programmable memory (RAM) and further Input means for entering a value N representing a number of drops. The central processing unit (CPU) generates a control pulse mutual control of the valve means when the determined number of drops reaches the value N stored in the memory (RAM). Through the The operator has the option of choosing the value N given, the volumetric mixing ratio in which the additive is metered should be set.

An embodiment of the invention is also preferred Dosing device in which the counting and control unit one free programmable memory (RAM), in which a storage space for a Constant A is provided, which is the number of drops per switching cycle Additive to add valve means corresponds. By choosing for the value A is created another possibility on the Mixing ratio to influence and the device on different Adjust additives.

It has also been found to be advantageous that the counting and Control unit a central processing unit (CPU) and one free programmable memory (RAM), in which a work program for the computing unit is stored, the valve means mutually such controls that after a certain number of switching cycles of the valve means a so-called "test switching cycle" is carried out in which the additive leading second hose line is switched through until  it is ensured that the second hose line and that on this connected reservoir still contains a supply of additive. To this end there will be such a large number of drops in the switched position of the valve allowed that the drained volume detected by the light barrier Additive to the volume of the drip pipe and possibly in the valve means contained dead spaces in any case, even if due to Viscosity influences should only precipitate very small drops.

Furthermore, it is preferably provided that the metering device disposable includes the z. B. disposed of after contamination with blood. To these items designed as disposable parts can in particular two hose lines, the two valve means, the drip pipe and the Include drip chamber. In this way, a hygienically perfect manageable device created in which the expensive parts, such as the Photoelectric sensor components and the counting and control unit that no pollution and are not subject to wear, are retained, however those with the fluid in Touching parts can be replaced quickly and easily, which is particularly fast and efficient in hospital operations Handling very accommodating.

The interchangeability, especially one designed as a disposable part The drip chamber and the Light barrier should preferably be designed so that the drip chamber in the appropriately trained light barrier components can be locked. This is preferably done in that the drip chamber in the form Component containing light barrier is latchable, d. that is, in the housing of the A cutout is provided in the light barrier, in which the partially transparent trained drip chamber can be snapped into place. The drip chamber can in particular be made from a plastic using injection molding technology.

The invention is illustrated below with reference to two in the drawing preferred embodiments explained in more detail.

The drawing shows:

Fig. 1 is a schematic representation of a first embodiment, and

Fig. 2 is a schematic representation of a second embodiment of a metering device according to the invention.

The embodiment of a metering device according to the invention shown in FIG. 1 is generally designated by reference number 10 . It has a first hose line 11 and a second hose line 12 . The two hose lines 11 and 12 meet at a Y-shaped junction 14 and merge into a drip pipe 16 . A drip chamber 18 adjoins the drip pipe and is supplied with a negative pressure via a discharge line 20 . Combined valve means in the form of a 4/2-way valve 22 are inserted into the two hose lines 11 and 12 . The 4/2-way valve is held in a rest position by a compression spring 24 , in which the first hose line 11 is switched to passage, while the second hose line 12 is blocked. The 4/2-way valve 22 can be actuated electrically by means of a solenoid 26 , so that the first hose line 11 is blocked in the switching position then assumed, while the second hose line 12 is connected to the drip pipe 16 .

In the state shown in FIG. 1, in which the valve 22 is in the rest position, the first hose line 11 is switched to passage. The negative pressure acting in the drip chamber 18 , which is applied via the discharge line 20 , acts via the drip pipe 16 and the valve 22 into the hose line 11 , which has a perforated end section 28 . The end section 28 of the hose line 11 is, for example, in a surgical wound and sucks blood and / or wound fluid there. The suctioned blood is conveyed through the hose line 11 and the valve 22 switched to passage and drips at the end of the drip tube 16 into the drip chamber 18 .

The falling drops interrupt the light beam, which is emitted transversely to the drip direction, of a light barrier 30 which is designed to surround the drip chamber. The light barrier 30 is constructed in a conventional manner and comprises, for example, a light-emitting diode (LED) 32 as the light source and a photo transistor 34 as the receiver element. A falling drop 36 darkens the phototransistor 34 illuminated by the light-emitting diode 32 , as a result of which a pulse is generated which is fed to a central processing unit (CPU). The pulses generated by the falling drops 36 are added up in the computing unit and compared with a setpoint N stored in a freely programmable memory (RAM). The setpoint can be 7, for example. After 7 drops have fallen, the central processing unit (CPU) generates a control pulse, which is fed to the solenoid 26 of the valve 22 in a correspondingly increased manner, whereupon the latter switches and blocks the hose line 11 , but releases the hose line 12 . At the upper end of the hose line 12 there is a reservoir 36 which contains an anticoagulant liquid (ACD), and optionally further additions of a sedative accelerator which increases the volume of the erythrocyte aggregates contained in the blood and thus sedimentation, ie separation of blood plasma and possibly contained Accelerated wound fluid, lymphatic water or the like.

The hose line 12 is connected through the now open valve 22 directly to the drip tube 16 , which is still filled with blood at this time due to the capillary action. As soon as a further drop 38 falls at the lower end of the drip tube 16 , a corresponding volume of ACD (anticoagulant liquid) is drawn from the hose line 12 at the upper end of the drip tube via the switched valve 22 . Since the volume replaced at the upper end of the drip pipe corresponds exactly to the volume that was released in the form of drops at the lower end of the drip pipe, the size of the drop leaving the drip pipe has no influence on the mixing ratio, which in the present example, for example, is 7: 1 by volume is.

After a further falling drop 38 has been detected by means of the light barrier and the central processing unit (CPU), the CPU generates a further control pulse with which the excitation current of the solenoid 26 is switched off, whereupon the compression spring 24 puts the 4/2-way valve into its rest position suppressed so that the tubing 11 is connected to passage and more blood is drawn through the drainage hose. 11

In order to ensure that the reservoir 36 for the anticoagulant fluid is still filled, it can be provided, after a certain number of switching changes, to keep the switching valve 22 in the switching position not only for the duration of a dropping drop 38 , but for a number of falling drops To keep drops in the switching position switching through the hose line 12 , which is dimensioned such that the total volume of the falling drops is slightly larger than the inner volume of the drip tube 16 plus any dead spaces in the valve 22 . In this way it can be ensured that anticoagulant liquid is still contained in the reservoir 36 .

A corresponding CPU-controlling device can be used to control this routine Program must be stored in the memory (RAM).  

To increase the concentration of anticoagulant fluid in the blood counter that caused by such dosing of anticoagulant fluid result for test purposes, it can be provided the value N for the normal Switching cycles increase accordingly, so that the overall mixture ratio between blood and anticoagulant fluid in the collection container that adheres to the drip chamber connects after a finite number of switching cycles of the Valve despite the additional addition of anticoagulant fluid during the "test cycle" again the originally intended mixing ratio corresponds.

The decisive influencing variable is the number of drops that are necessary to measure a volume that is certainly larger than the volume of the drip tube plus the volume of any dead spaces in the valve 22 , even in the worst case, that the smallest conceivable drop size is produced because, for example, the viscosity of the blood has an unfavorable influence. A drop falling beyond this number then indicates that ACD is still present.

This number can be influenced by the dimensioning of the drip pipe. Furthermore, the number of switching cycles which are run through before a “test switching cycle” is carried out, in the course of which the switching valve 22 remains in the switching position longer than only for a falling drop, ie with the anticoagulant liquid line 12 switched on .

If, for example, a mixing ratio of 7: 1 is desired, the valve 22 will remain in the rest position for seven drops 38 falling at a normal rhythm, ie without a test cycle, and then switch to the switching position for one drop.

Assuming that every tenth switching cycle is to be a test switching cycle in which a total of eleven drops fall through the drip chamber while anticoagulant liquid is drawn through the valve 22 in the switching position, the number of drops that fall while the switching valve is in the rest position, that is, while the hose 11 is switched to passage, to fourteen.

After ten complete switching cycles, there are a total of one hundred and forty Drops of blood moved into the drip tube during the nine normal switching cycles nine drops of anticoagulant fluid and in the tenth Switching cycle eleven drops of anticoagulant fluid have been added. The total mixing ratio is therefore 140:20, i.e. H. 7: 1 as without Test switching cycle.

Due to the easily understandable relationships, appropriate dimensioning of the drip pipe or the number of normal switching cycles or the mixing ratios other Find numerical ratios that use a described one Allow test switching cycle without changing the mixing ratio. According to the invention has a changing drop size due to changing Viscosities have no influence on the mixing ratio.

It can be provided that the drip chamber 18 is designed as a disposable part which is coupled together with hoses 11 and 12 also made of plastic and a valve made of simple plastic components.

In FIG. 2 a circuit-technically more complex variant of the dosing device according to the invention, 2-way valve is a 3/3-way valve is used in place of a 4 /. The remaining components and elements correspond to the embodiment shown in FIG. 1, the same parts having the same reference numerals, so that the description in this regard is not repeated.

The 3/3 Wegevenffl 23 in Fig. 2 has two compression springs 24 'and 24 '', by means of which it is centered. In the rest position of the 3/3-way valve 23 shown , both the hose line 11 and the hose line 12 are blocked, so that no liquid can reach the drip pipe connected to the third connection of the 3/3-way valve. In operation, a switching signal is generated by the CPU, which is appropriately amplified to a first solenoid 26 ', so that the 3/3-way valve 23 is switched to a first switching position in which the drainage or hose 11 is connected to the drip pipe 16 is, while the hose line 12 carrying the anticoagulant liquid remains blocked. In this embodiment of the invention, the two hose lines 11 and 12 are therefore not directly coupled to one another at a junction, but are indirectly connected to one another by the 3/3-way valve 23 . After a predetermined number N, the CPU generates a switching pulse again, which this time is fed to the solenoid 26 with corresponding amplification, whereupon the 3/3-way valve is pressed into a second switching position in which the hose line 12 is connected to the drip pipe 16 , so that another falling drop 38 pulls anticoagulant liquid into the drip tube 16 .

Referring to Fig. 2 it will be seen that the dosing device of the invention can also be realized with a 3/2-way valve. If one thinks away in Fig. 2, the middle, spring-centered rest position of the 3/3-way valve, two switching positions of a 3/2-way valve remain. In such an embodiment, the compression spring 24 '' and the left solenoid 26 'would be omitted, so that the remaining compression spring 24 ' presses the 3/2-way valve into a rest position, in which the hose 11 is connected to the drip pipe 16 . After a corresponding number of fallen drops N, the CPU generates a corresponding switching pulse, which is used to apply an excitation current to the solenoid 26 '', so that the 3/2-way valve is switched to a switching position in which the anticoagulant fluid is leading Hose line 12 is connected to the drip pipe 16 .

As further indicated in the figures, the light barrier 30 is installed in a housing which has a groove-like recess 40 . The appropriately designed drip chamber 18 can be snapped into this recess 32 in a form-fitting manner. The drain line 20 , the drip chamber 18 , the drip pipe 16 , the valve 22 and 23 and the two hose lines 11 and 12 can be designed as disposable parts that can be easily replaced when the device, ie the parts to be recycled, such as light barrier 30 in particular , CPU and RAM are to be used in another operation, for example.

The metering device according to the invention allows an exact volumetric Addition of an additive without changing the droplet size from drops detected and counted by means of a light barrier has the accuracy of the dosage.

Reference list

10 dosing device
11 first hose line
12 second hose line
14 junction (from 12 to 11 )
16 drip pipe
18 drip chamber
20 exhaust line
22 4/2-way valve
23 3/3-way valve
24 , 24 ' , 24'' compression spring
26 , 26 ′ , 26 ′ ′ solenoids
28 perforated end section (of 11 )
30 light barrier
32 light emitting diode
34 photo transistor
36 reservoir
38 drops
40 recess (in 30 )

Claims (12)

1. dosing device ( 10 ) for volumetric dosing of a liquid additive, which is added to a fluid flowing in a first hose line ( 1 ) via a second hose line ( 12 ) in a certain volume ratio, in particular for the volumetric dosing of an anticoagulant liquid (ACD) or a sedimentation accelerator in a system for collection and retransfusion of autologous blood,

• - With electrically controllable valve means ( 22 ; 23 ), which are inserted in both hose lines ( 11 , 12 ) and alternately switch only one of the two hose lines to a downstream common hose or pipe section ( 16 ), and
• - with a counting and control unit (CPU, RAM),

characterized in that the common hose or tube section is designed as a drip tube, a drip chamber ( 18 ) is connected downstream of the drip tube, the counting unit by means of a light barrier ( 30 ), the direction of action of which is arranged transversely to the drop distance of the drops which are in the drip chamber ( 18 ) falling drops counts and the control unit reverses the valve means after a certain number of drops. 2. Dosing device according to claim 1, characterized in that the valve means are a 4/2-way valve ( 22 ). 3. Dosing device according to claim 1, characterized in that the Valve means are a 3/2-way valve.   4. Dosing device according to one of claims 2 or 3, characterized in that the valve ( 22 ) is spring-loaded, the first hose line ( 11 ) being switched to passage in the rest position. 5. Dosing device according to claim 1, characterized in that the valve means are a 3/3-way valve ( 23 ) which has a spring-centered center division in which both hose lines ( 11 , 12 ) are blocked. 6. Dosing device according to one of the preceding claims, characterized in that the counting and control unit comprises a central processing unit (CPU) and a freely programmable memory (RAM) and input means for entering a value N representing a number of drops, and that the central processing unit (CPU) generates a control pulse for mutual actuation of the valve means ( 22 ; 23 ) when the determined number of drops reaches the value N stored in the memory (RAM). 7. Dosing device according to one of the preceding claims, characterized characterized in that the counting and control unit one free programmable memory (RAM), in which a storage space for a constant A is provided which corresponds to the number of drops per Switching cycle of the additive to be added to the valve means corresponds. 8. Dosing device according to one of the preceding claims, characterized in that the counting and control unit has a central processing unit (CPU) and a freely programmable memory (RAM) in which a work program for the processing unit is stored, which the valve means ( 22 ; 23 ) controls each other in such a way that after a certain number of switching cycles of the valve means, a switching cycle is carried out in which the second hose line ( 12 ) carrying the additive is switched through until the volume of additive which has flowed through the light barrier ( 30 ) is detected corresponds to the volume of the drip pipe ( 16 ) and any dead spaces contained in the valve means ( 22 ; 23 ) (test switching cycle). 9. Dosing device according to one of the preceding claims, characterized in that the two hose lines ( 11 , 12 ), the valve means ( 22 ; 23 ), the drip tube ( 16 ) and the drip chamber ( 18 ) are designed as disposable parts. 10. Dosing device according to claim 9, characterized in that the drip chamber ( 18 ) and the light barrier ( 30 ) are designed so that the drip chamber designed as a disposable part can be locked in the correspondingly designed light barrier components. 11. Dosing device according to claim 10, characterized in that the drip chamber ( 18 ) can be snapped into the component contained in the light barrier ( 30 ).